Pressureless sintering of silicon nitride with Magnesia and Yttria

Si3N4-MgO-Y2O3 ceramic materials have been fabricated by pressureless sintering, which overcomes the limitations of hot pressing. The amount of Y2O3 has a strong influence on the densification behavior and mechanical properties of the sintered materials. The pressureless sintered silicon nitride with 5 wt.% MgO + 4 wt.% Y2O3 achieved a relative density of 99%, a bending strength of 950 MPa and a fracture toughness of 7.5 MPa m−1/2.